Farhan, Ahmed Hilal

457 Pages·2017·24.36 MB·English

by  Christine Middleton

Farhan, Ahmed Hilal (2016) Characterization of
rubberized cement-stabilized roadbase mixtures. PhD
thesis, University of Nottingham.
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Facultyof Engineering–Civil EngineeringDepartment
Characterization of Rubberized Cement-Stabilized
Roadbase Mixtures
By
Ahmed Hilal Farhan
B.Sc. Civil Eng., M.Sc. Highways and Airports Eng.
Thesis submitted to the University of Nottingham for the degree of
Doctor of Philosophy in Civil Engineering
April2016
i
Abstract
Due to urbanization, industrialization and population increase, a substantial increase
occurred in the number of vehicles and hence large numbers of end-of-use tires are being
disposed every year. The vast majority of these tires are stockpiled or used as a fuel for
combustion which, in both cases, affects the environment detrimentally. The use of tire
rubber in cement-stabilized aggregate mixtures (CSAMs) will ensure beneficial use of large
quantities of these waste materials, saving natural resources and may enhance the properties
ofCSAMsespeciallytheserelatedtobrittlenessandsensitivitytofatiguefailure.
Research was undertaken to investigate, at macro and mesoscale levels, the effect of both
rubber and degree of stabilization and their combination on the behaviour of CSAMs in
terms of the most influential pavement design properties under different static and dynamic
modes of loading. These properties are strength, stiffness and fatigue. A range of testing
equipment, methodologies and tools was developed, suggested and implemented to perform
this investigation. Further investigation was also conducted to provide better understanding
of the damage and failure mechanism through quantitative studying of the fractured surface,
internalstructureandsurfacecrackingpatternsunderdifferenttestingmodes.
The results of this study revealed that the addition of rubber has a negative effect on the
compaction efficiency, compressive, flexural and tensile strengths while the stiffness, under
different testing modes, was slightly reduced. In addition, a tougher mixture was produced
after rubber-modification which means a change from a brittle to a more ductile behaviour.
Thisbehaviourwasobservedthroughdifferentstiffnessmodulusevaluationmethods.Onthe
other hand, increase in cementation level has resulted in an increase in both strength and
stiffness for both reference and rubberized mixtures. However, the decrease in the mixtures’
strengthdue torubberizationwas more obvious inhighlycementedmixtures thanthe lightly
cemented ones. On the other hand, a greater decline in the mixtures’ stiffness, due to rubber
incorporation, was observed at low cement contents. This behaviour is related to the void-
like behaviour which depends, to large extent, on the relative stiffness between rubber and
surroundingmatrix.
ii
Quantification of the fractured surfaces and cracking pattern utilizing the photogrammatry
and fractal dimension concepts, respectively, revealed that the addition of rubber resulted in
rougher and more tortuous cracks and increases disperse-ability of these cracks. This means
the rubber-modification changed the cracking pattern which implies better load transfer
throughthecracksandlessriskofreflectioncracking.
The investigation of the internal structure, at mesoscale level, showed that the cracks were
propagated through the rubber particles at all investigated cementation levels. This
contributed to a lengthening of the crack path and to the delaying of crack propagation by
absorbing and relieving the stresses at the crack tip, especially at the microcrack level. The
latter mechanisms are behind toughness and fatigue improvement. Evaluation of rubber
distributionrevealeduniformdistributionandthisdecreaseasrubbercontentincreases.
The results also indicated an improvement in the fatigue life for all rubber replacement
levels. This was valid at all cementation levels. In terms of modulus degradability,
rubberization of the cemented mixture has only a slight effect on this property while larger
permanent deformation was accumulated after rubber inclusion. It was observed that the
poorly cemented mixtures showed greater stiffness modulus degradation. Pavement analysis
and design study showed that the decrease in the mixtures’ strength overshadowed any
improvement due to both mitigation of mixtures’ stiffnesses or fatigue life enhancement.
However, this is not the case for poor rubber mixtures where this mixture showed better
behaviourthanthereferencemixtures.
iii
Dedication
At the feet of my mother and my father
iv
Acknowledgement
All thanks, glory, praise and adoration is due to God almighty, the most gracious the
most merciful. O Allah you gave me the patience and strength to tackle with the
hardships Ihave facedand guidedmetofinish this research.
First of all I would like to express my deep thanks for my supervisors: Mr. Andrew
Dawson and Dr. Nick Thom for their motivation, encouragement and guidance
throughout this project. I can say that I still hear your encouragement statements
which indeed were like a charger to continue in this project after many difficulties
that I faced. Big thank is also due to Mr. Andrew (particularly) due to his effort in
reviewing my thesis chapters. They really gave me an excellent experience. Mr.
Andrew and Dr. Nick I would say I am sorry for the many virtual five minutes that I
frequently took during my PhD program to discuss some issues which always
becomehalf anhour.
I appreciate the kind advices from Dr. Luis Neves, myinternal assessor, especiallyat
thebeginningofthis project.Thanks Dr. Luis for yourkindness andencouragement.
Sincere appreciation is due to the Higher Committee for Education Development in
Iraq(HCED)forprovidingascholarshiptoconduct this PhDstudy.
At this point, I can say that conducting such research with this type of mixture that
share some properties of concrete (as cementitious material) and the others with the
asphaltic mixtures (as a compacted material with relatively small stabilizer content)
used in pavement structure is not an easy task. This is because this requires an
understanding of both cement and asphalt concrete mixtures as well as cement-
stabilized mixtures and their testing and most importantly higher level of
independency in terms of sample manufacturing and testing. The independency in
conducting this research was quit hard and useful at the same time. No doubt this
comprehensive studyrequireddifferent tests andtools at different places. So, Iwould
liketothankthefollowingpeoplewhohelpedme bydifferent means:
v
 Mr. Nigel Rook (concrete laboratory) for his kindness by providing cement,
moulds andsometechnical demonstration(at thestart ofmystudy).
 Balbir Loyla (structures laboratory) for helping during the development of
fatigue testing machine, kind advices to start with instrumentation process and
forstrain gauging.
 Mr. Richard Blackmore (Nottingham Transportation Engineering Centre-
NTEC)forhis technical discussionanddemonstration.
 Mr. Jon Watson (NTEC) for his friendship, helping in X-raying some trials and
scanningsomesamples andhis continuous encouragement andsupport.
 Mr. Steve Elesbrook (Servocone Company) for his technical advice (in spite of
his extremelylimitedtime)duringmystrugglingwithcyclictestingfacility
 Mr.Andrew Cooper(CooperCompany)forhis cooperationanddiscussionwhen
IstartedusingtheNAT machinetocharacterizemystiffmixtures.
 Mr. Tom Buss (senior technical manager at the Faculty of Engineering) for his
technical discussionduringsometesting.
 Mr. Martyn Barret, Mr. Mathew Thomas and Miss. Laura (all from NTEC) for
theirhelpinsamples trimming.
 Mr. Mark Dale (rock mechanics laboratory) for coring and testing my rock
samples.
Thanks must go toDr. MathewHall (theUniversityofNottingham)forprovidingme
with the waste rubber and due to his discussion during my flexural program. Special
thanks are also extended to Prof. Kypros Pilakoutas and Dr. Harris Angelakopoulos
(both from Sheffield University) for providingme with some materials and their kind
encouragement at the beginning of this project. Also, I am grateful to Dr. Martin
Smith (Geospatial Institute at the University of Nottingham) and Dr. Sarhat Adam
for their cooperation and involving me in scanning of myfractured surfaces samples.
I must appreciate the help from Mr. Chris Fox (senior technician at Faculty of
Engineering) for scanning some of samples. Special thanks to Dr. Alvaro Garcia for
his friendship and support. I also appreciate the support from Dr. James Grenfell for
helping in some ITS trials. Myappreciation also goes to Mrs. Kathryn Sanderson for
her encouragement and support in my conference administrative work. I must give
special thanks for the reviewers of my papers for providing me with a useful
feedbackthat contributed toraisethequalityofthis PhDstudy.
vi
Thanks is also to my colleagues at the Nottingham Transportation Engineering
Centre Dr. Ameer, Dr. Mahmood Al-Nasri, Dr. Chibuzor, Ahmed Nassar, Waleed,
Ayad, Gustavo, Dr. Mahmoud, Rami, Bilal, Sydney, Venon, Hamed, Ahmed
Ibrahim, Hasan, Abdulshafi, Yasameen, Haneen, Harith and Tariq. I am grateful to
Dr.Ameerforhis helpwhen Ifirst cametotheUK.
I would like also to thank Dr. Jamal A. Farhan, the Assistance Prof. at Al-Anbar
University for his continuous support and encouragement during my academic and
practical lives and for keepingintouchduringmyPhDstudy. Also, Iam grateful due
Dr.Juma’ahAl-Sumaida’ai forhis encouragement.
Now it is the time to thank my wife and my daughter: the tax payers of my success.
Youreallystruggleda lot (especiallymydaughter Haya) duringmyPhDstudy. Haya
I know that I was not a perfect father because of my busy time but I will be a father
to be proud of. All thanks to my mother and my father for their prayers and
encouragements during the whole of my life. I have also to give big thanks to my
brothers and my sisters for their support during my study. Finally, I would say I am
sorry for both my big and small families because I know that the three years of my
studywithout anyvisit tomycountry,duetomycontinuous workinthis project,was
hardandlongtimeforbothof you.
vii
Declaration
This research described in this thesis was conducted at the Civil Engineering
Department, the University of Nottingham between October 2012 and February
2016. I declare that the work is my own and has not been submitted for a degree at
anotheruniversity.
AhmedHilal Farhan
TheUniversityofNottingham
viii
Table of Contents
Abstract
Dedication
Acknowledgement
Declaration
Tableofcontents
List offigures
List oftables
List ofabbreviations
List ofnotations
Chapter1................... Introduction …………………….……………...……… 1
1.1 Backgroundandproblem statement……………………………………..1
1.2 Aim andobjectives …………………………………...……….………...6
1.3 Noveltyofresearch…………………………………………………..….8
1.4 ResearchMethodologyandstructureofthesis …………………...……..9
1.5 Researchsignificanceandcontribution………………………....………13
1.6 Publications, Prizes andachievements...............................................…...16
1.7 References……………………………………………………….…….....18
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